How do you calculate the daily periodic rate on a credit card?

To calculate the daily periodic rate on a credit card, divide the annual percentage rate by 365, the number of days in a year. For example, an 18 percent annual rate produces a daily periodic rate of about 0.0493 percent.

Periodic Interest Rate Calculator: Find Rate Per Period

Periodic Interest Rate Calculator

Convert a nominal annual interest rate into the exact rate per compounding period in seconds.

Annual rate (R) in percent

This is the nominal or stated interest rate.

Compounding periods (m)

Number of times compounding occurs per year.

Common periodic interest rate reference examples
Annual rate (R)	Compounding	Periods (m)	Periodic rate
18%	Daily	365	0.0493%
12%	Monthly	12	1.0000%
6%	Quarterly	4	1.5000%
9%	Quarter, compounded monthly	3	3.0000%
24%	Monthly	12	2.0000%
5%	Semiannual	2	2.5000%

Periodic interest rate explained simply

Periodic interest rate explained simply means taking the stated annual interest rate and spreading it evenly across each compounding period within the year. This periodic rate is the figure actually applied to a balance every time interest is calculated, whether that happens daily on a credit card or monthly on a loan.

The periodic interest rate formula

The periodic interest rate formula divides the nominal annual rate by the number of compounding periods to find the rate applied at each individual period.

P = R ÷ m

In this formula, R is the nominal or stated annual interest rate in percent, and m is the number of compounding periods occurring within that same time frame. The result, P, is the effective rate charged or earned during each individual compounding period.

Worked example of periodic interest rate

A worked example of periodic interest rate shows how a credit card’s annual rate translates into a daily charge. Suppose a credit card carries an 18 percent annual interest rate compounded daily across 365 days.

P = 18 ÷ 365

P = 0.0493%

The daily periodic rate on this credit card balance is approximately 0.0493 percent, which is the rate actually applied to the balance every single day.

How to use this periodic interest rate calculator

How to use this periodic interest rate calculator only requires two numbers, the annual rate and the number of compounding periods. Enter both values and select Calculate to see the periodic rate instantly.

Enter the nominal annual interest rate as a percent.
Enter the number of compounding periods within that time frame.
Select Calculate to view the periodic interest rate and the full working steps.
Select Clear to reset the calculator and try different values.

Periodic rate versus effective rate

Periodic rate versus effective rate is an important distinction when comparing loans or investments. Periodic rate is the simple division of the nominal rate by the number of periods, while effective rate accounts for the compounding effect across all periods, which makes the effective annual rate slightly higher than simply multiplying the periodic rate by the number of periods.

Periodic rate answers what rate applies during a single compounding period.
Effective rate answers what the true annual cost or return becomes after all compounding.
The gap between the two grows larger as compounding frequency increases.

The interest rate can apply to any time unit, not only a year, as long as the rate and the number of compounding periods refer to the same overall time frame.

Real world uses for periodic interest rate

Real world uses for periodic interest rate appear most often in credit cards, mortgages, and savings accounts. Credit card issuers use the daily periodic rate to calculate finance charges, mortgage lenders use the monthly periodic rate to determine payment schedules, and savers use the periodic rate to understand how often their balance actually grows.

Calculating daily finance charges on a credit card balance.
Determining the monthly periodic rate used in mortgage amortization schedules.
Comparing savings accounts that compound at different frequencies.
Converting a quarterly stated rate into an equivalent monthly periodic rate.

Frequently asked questions about periodic interest rate

The periodic interest rate formula is P equals R divided by m, where R is the nominal annual interest rate and m is the number of compounding periods within that same time frame.

To calculate the daily periodic rate on a credit card, divide the annual percentage rate by 365, the number of days in a year. An 18 percent annual rate produces a daily periodic rate of about 0.0493 percent.

Periodic rate is the simple division of the nominal annual rate by the number of compounding periods. Effective rate accounts for the compounding that occurs across all periods within a year, which makes the effective rate slightly higher than the periodic rate multiplied by the number of periods.

No, the periodic interest rate is not the same as the nominal rate. The nominal rate is the stated annual rate, while the periodic rate is that nominal rate divided across the number of compounding periods within the year.

Yes, periodic rate can be calculated for any consistent time unit, such as a quarterly rate compounded monthly, as long as the nominal rate and the number of compounding periods refer to the same overall time frame.

Enter the nominal annual rate and the number of compounding periods per year into a periodic interest rate calculator, and it instantly divides the rate by the number of periods to give you the periodic rate.